We (humanity) have gotten comfortable with the way things are, and a change in that is going to mean that things are going to change for us, and we don't like change. Most of our biggest cities are all close to the coast and will be subject to massive flooding in the next 100 years (if not sooner). Much of those same large population centers are also fairly close to being too hot for general survival (without aggressive AC). Our agriculture is all setup for the temperatures we have now, and the rain patterns we are used to. So we are going to have to change both where we live, and how we grow our food (location and probably strains as well).
Global warming is (almost) definitely not going to destroy all life on earth, but many of the forecasts are in extinction-level for most of the large animals. So life in general will continue, and probably humanity (since we are so good at making environment for ourselves), but the (eventual) changes are going to make the world very different, in ways that we are not going to like.